Size vapor barrier materials for slabs, crawlspaces, and walls accurately every time. Compare overlaps, seam tape, and pricing, then download reports instantly for you.
Choose a method, then enter dimensions, overlap, waste, and pricing.
| Scenario | Area | Overlap | Waste | Roll | Estimated Rolls |
|---|---|---|---|---|---|
| Small under-slab room | 600 sq ft | 10% | 5% | 12 in × 100 ft | 6 |
| Crawlspace cover | 900 sq ft | 12% | 8% | 24 in × 75 ft | 6 |
| Wall moisture protection | 800 sq ft | 15% | 7% | 48 in × 50 ft | 4 |
The calculator estimates required barrier coverage by applying overlap and waste factors:
If the layout estimator is enabled, it first approximates the installed sheet area using roll strips:
Rolls needed are calculated by dividing required area by roll area and rounding up.
Moisture migrating from soil or humid voids can raise indoor humidity, damage finishes, and reduce insulation performance. A vapor barrier limits diffusion and capillary evaporation, helping protect flooring systems, framing, and stored materials in crawlspaces.
Under-slab installations reduce ground moisture entering concrete. Crawlspace liners reduce evaporation from exposed soil and help stabilize relative humidity. Wall applications support assemblies where the design calls for controlled vapor movement.
Products are often specified by thickness (mil). Thicker sheets generally resist punctures better during placement and service. Typical residential liners may range around 6–20 mil, while demanding sites can specify heavier membranes with reinforcement.
Overlaps consume extra material and can be a meaningful share of total coverage. Many crews plan overlaps in the 6–12 inch range at seams, plus extra for penetrations, grade changes, piers, and repairs. The overlap factor field captures this impact.
Waste accounts for trimming, irregular geometry, roll changes, rework, and jobsite handling. A 5–10% allowance is common for cleaner layouts, while complex footprints or tight access can justify higher values. This calculator applies waste after overlap for conservatism.
When enabled, the layout estimator converts surface width into roll strips using an effective width (roll width minus overlap width). It then estimates seam length from strip count and surface length, producing a practical basis for seam-tape quantities.
Seam tape is typically applied along overlaps to reduce leakage paths. Perimeter sealing length adds the boundary run where the barrier turns up walls or terminates. Optional fastener counts provide a simple estimate for vertical installs or temporary anchoring needs.
Use “Required barrier area” to confirm coverage, then review “Rolls needed” and total estimated cost. If rolls are high, compare larger roll widths, reduce unnecessary overlap, or adjust waste to match site realities. Always confirm details against project specs.
Start with 10% for straightforward rectangles. Increase for many penetrations, tight corners, or higher seam requirements. If you also enter overlap width and enable layout mode, the calculator refines seams separately.
Use room mode when you know dimensions and want seam/perimeter estimates. Use total area mode when you already have measured coverage and only need roll and cost totals.
It models the surface as roll strips and counts seams. This can increase material use versus simple area factors, especially when roll width is small relative to the surface width.
No. It is an estimating tool. Always follow your drawings, membrane class requirements, and manufacturer installation guidance for seam treatment, terminations, and compatibility.
Perimeter sealing helps control moisture entry at edges and terminations. It can be significant in crawlspaces and at slab perimeters where the barrier is turned up or sealed to walls.
Fasteners are common for vertical sections, temporary holds, or liner attachment systems. If your installation is fully weighed down or mechanically clamped, you may not need them.
Yes. After calculating, use the CSV or PDF buttons in the results panel. The export reflects your last completed calculation and is ready for quoting or documentation.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.